The present invention relates to a magnetic head of a thin-film structure and more particularly relates to such a head which can be operated at an improved high recording efficiency.
The recent tendency toward increased high-density requirements in the art of magnetic recording calls for introduction of a smaller track width such as below 20.mu. and a greater operating frequency such as 10 MHz or more. In the light of these problems of manufacturing and function, possibilities of conventional magnetic head construction using such bulk material as ferrite are very limited, and accordingly thin-film magnetic head techniques are much called for.
A conventional method used in constructing a thin-film magnetic head composed of electrically-conductive, insulating, and magnetic thin films is such that, as shown in FIG. 1A and 1B, an electrically-conductive material layer 1 is formed on a base magnetic layer, that is, a magnetically-flat magnetic substrate 2 or a magnetic thin-film layer, with an insulating layer 3 interposed therebetween, and a magnetic thin-film layer 4 is laid on the top, with an insulating layer 5 interposed between the conductive material layer 1 and magnetic thin-film layer 4, forming an operating gap area A at the front portion.
In such a construction, the magnetic layers 2 and 4 adjacently face each other and the magnetic layer 4 is substantially thin; and these facts are likely to cause magnetic saturation and make it difficult to operate such a head in with sufficient efficiency as a recording head. Moreover, if such a thin-film magnetic head is to be employed for both recording and reproducing operations, it is necessary to increase the number of windings in order to obtain sufficient reproducing voltage. However, since multi-layer construction of the windings may entail a number of manufacturing problems such as increased number of processes and decreased yield, it is desirable to have the windings formed in a plane. Thus, the length of magnetic core portion crossing over windings tends to expand, resulting in a decrease of core efficiency for a magnetic head because of increased magnetic flux leakage.
Where the width of a magnetic layer 4 is uniformly distributed as shown in FIG. 1, the magnetic flux distribution in the magnetic thin-film takes such a pattern as seen in FIG. 2. That is, flux .phi. is at its maximum value .phi..sub.m at the rear junction where Y=0 and diminishes substantially before it reaches the operating gap at the front end. This means that the magnetic flux is not effectively transferred to the operating gap.
To overcome this difficulty, it is desirable to obtain a uniform distribution of magnetic fluxes over the region in which a conductor layer used for the windings is present, so that magnetic fluxes at such a uniform value can be passed on to the operating gap.
As an approach to solve such problem, there has been proposed to use a thin-film magnetic head of such a type as shown in FIG. 3. This thin-film magnetic head is such that there is provided a groove 6 in a magnetic substrate 7, the groove 6 being filled with non-magnetic materials 8 such as glass and an electrically conductive material, whereby the distance between the opposed part enclosing the conductor layer 1 of the magnetic substrate 7 and the magnetic layer 4 is enlarged so as to reduce magnetic flux leakage and thereby improve magnetic core efficiency. With the exception of the above point, the magnetic head is of same construction as that shown in FIG. 1.
Even with such a thin-film magnetic head, however, it was difficult to obtain sufficient recording efficiency.